The present invention relates to a device for scarifying the interior surface of a pipe and, more specifically, for scarifying the interior surface of a sewer pipe by removing corrupted material from the interior surface of the sewer pipe.
Pipes used to carry liquids and gases commonly transport all types of materials including water, natural gas, solid and liquid sewage, as well as various other accumulations from the pipe. Over time, these pipes require servicing and cleaning. Taylor et al. disclose automated systems for cleaning the outside of a pipeline in U.S. Pat. No. 5,520,734. Taylor et al. excavate under subterranean pipe and restore it by first cleaning the pipe and then applying a protective coating to the outer surface. As yet, however, nobody has automated a process for cleaning or restoring the inside of a pipe.
The interior surface of a pipeline carrying solids, liquids and gases generally degrades over time as the pipe walls interact chemically and physically with the substances flowing through them. In particular, a sewer system""s interior walls corrode and deteriorate because corrosive materials contaminate the surface degrading the metal and concrete used to build the sewer. The corrosive material arises from both the sewage and waste water itself, and also from the digestive by-products of bacteria found in the sewage which proliferate in the anaerobic environment. The corrosion causes the walls of the sewer pipe to physically decay, eventually reducing their overall thickness.
The principal source of corrosion is sulfuric acid, which arises as a product of the materials transported in a sewer pipe and the sewer environment itself. Various metal sulfates found in the sewage quickly convert into hydrogen sulfide by: reducing to sulfide ions in the waste water, combining with hydrogen in the water and outgassing above the liquid as hydrogen sulfide gas. Additional hydrogen sulfide originates from bacteria containing contaminants which accumulate on the relatively rough concrete below the maximum liquid level. Bacteria found in these accumulations thrive in the anaerobic sewer environment producing hydrogen sulfide gas as a respiratory bi-product. Oxygen from the liquid below and oxygen condensing from the water in the air react with the hydrogen sulfide on the pipeline walls creating the highly corrosive sulfuric acid. The sulfuric acid attacks the calcium hydroxide in the concrete sewer walls leaving calcium sulfates which ultimately crumble and fall off of the interior of the wall substantially reducing its thickness.
The waste water level varies over the course of a 24 hour period. The flow is at its lowest level between 1:00 AM and 6:00 AM in the morning but it rises distinctly in the daytime and the pipe may operate near capacity. Because of the gaseous nature of the hydrogen sulfide, the pipe walls are predominately corroded in the portions of the wall above the minimum liquid level. Portions of the walls which are always below the water level are not subjected to such high concentrations of hydrogen sulfide gas or sulfuric acid and consequently do not experience the same levels of decay.
Eventually the sewer walls must be restored or they can suffer permanent damage leading to great expense. The restoration process is a two step operation that consists of first cleaning all of the contaminants (and possibly outer layers of corrupted concrete) from the surface of the pipe and then applying a protective coating over the newly cleaned pipe surface. Attempting to apply a protective coating without first cleaning the pipe surface is futile because it does not stop the decay that has already began underneath the coating. Furthermore, the protective coating itself does not adhere well to the contaminated surface. Thus, cleaning is an essential element of the restoration process.
As previously mentioned, a sewer system typically operates at high capacity during the day with decreasing flow overnight. In order to restore the sewer pipes without diverting the flow (a costly and sometimes impossible alternative), a bulk of the work must be done at night during the brief period when the flow is at a minimum. As previously outlined, the restoration process involves both cleaning the pipe surface and applying a protective coat. In practice, the rate of restoration is impaired because manual cleaning takes a proportionally greater amount of time than does the application of the protective coat. Consequently, a need exists for an automated cleaning process. Such a process will improve the rate of cleaning of the pipeline""s interior walls making restoration without diversion a cost-effective possibility. Further, automation of the process can help to ensure that the same intensity of cleaning is applied to the entire surface without the quality variation that is inherent in manual execution.
Several patents such as Taylor et al. (U.S. Pat. No. 5,520,734), describe automated processes for cleaning the outside surface of pipelines using spray nozzle jets; however, none have attempted to automate the cleaning of the interior surface of a pipeline.
According to the invention there is provided an apparatus for scarifying an interior surface of a pipe both of round and non-round cross section. The apparatus, which has a nozzle for discharging fluid under pressure against the interior surface of the pipe, also has a vehicle moveable along an interior of the pipe in a direction substantially parallel to an axis of the pipe, a principal arm coupled to the vehicle and a scarifying assembly rotatably coupled to the principal arm having a fluid nozzle assembly with at least one fluid nozzle. The fluid nozzle assembly is operative to one of rotate and oscillate, one of the scarifying assembly and the principal arm being longitudinally extendible to place the fluid nozzle at a location adjacent the interior surface of the pipe and operative, as the vehicle moves along the interior of said pipe, to remove contaminants and corrosion along a selected region along the interior surface of the pipe. The selected region is of an area larger than an area that would be scarified by the nozzle if it were not rotating or oscillating, when the fluid from the fluid nozzle assembly is directed as a jet against the interior surface of the pipe.
The scarifying assembly may have an exchanger couplable to a source of pressurized fluid, and a plurality of nozzle branches coupled to the exchanger and a plurality of nozzles affixed to a distal end of each of the nozzle branches. The exchanger, nozzle branches and nozzles may be operative to rotate relative to the vehicle and the exchanger may be operative to direct pressurized fluid into each of the nozzle branches and out of each of the nozzles as a jet stream of fluid capable of scarifying on impact the interior surface of the pipe.
The fluid nozzle assembly may include a plurality of branches mounted to a distal end of the arm, with the branches being rotatable about an axis parallel to an axis of the principal arm, and plurality of fluid nozzles, with each fluid nozzle attaching to a corresponding one of the branches. Each of the fluid nozzles is operative to expel a jet of pressurized fluid against the interior surface of the pipe. The principal arm is longitudinally adjustable to position the fluid nozzles at a desired position adjacent to the interior surface of the pipe.
The nozzle assembly may scarify a linear swath along the interior surface of the pipe along the direction of travel of the vehicle.
One of the principal arm and the nozzle assembly may be longitudinally extendible to locate the nozzles adjacent to a bottom surface of the pipe so that the pressurized fluid expelled from the nozzles impacts the bottom surface of the pipe.
The vehicle may have a chassis operative to support the scarifying assembly with a pair of spaced apart tracks positioned on either side of the chassis. The tracks may be operative upon rotation to propel the vehicle along a longitudinal direction in the interior of the pipe and may be laterally adjustable to accommodate various pipe sizes. A motor may be mounted on the chassis, may be coupled to the spaced apart tracks, and may be operative to rotate the tracks. A power coupler may be mounted on the chassis and couplable to a power source. The power coupler may be operative to conduct power to the apparatus.
The principal arm may be telescoping and pivotally attached to the vehicle and pivotal through an angle proximate 0 degrees to the horizontal when the vehicle is on a level surface to an angle proximate 180 degrees and a nozzle assembly affixed to a distal end of the principal arm, the nozzle assembly being one of rotatable and oscillatory about a longitudinally extending axis of the principal arm.
The power coupler may be operative to provide power to an actuator, and the actuator operative to move the scarifying assembly with respect to the vehicle.
The exchanger may be operative to use energy from the pressurized fluid to move the cleaning assembly with respect to the vehicle.
The scarifying assembly may further include a plurality of telescoping subsidiary arms rotatably mounted to the principal arm and a nozzle assembly mounted to a distal end of each of the subsidiary arms, each nozzle assembly being one of rotatable and oscillatory about an axis parallel to a longitudinally extending axis of each subsidiary arm and operative to emit jets of pressurized fluid outwardly away from the distal end substantially parallel to the longitudinally extending axis.
The principal arm may be removable from the vehicle and the tracks laterally adjusted towards each other to allow the vehicle to pass through access openings to the pipe.
In another aspect of the invention there is provided a method of scarifying an interior surface of a pipe to remove contaminants and corrosion products, using a self-propelled vehicle carrying an attached principal arm with a nozzle assembly at a distal end thereof. The nozzle assembly has a plurality of nozzles mounted at a free end of associated nozzle branches, the nozzle branches being rotatable or capable of oscillation about a distal end of the principal arm. The method includes positioning the nozzle assembly so that the nozzles are at a desired position adjacent a first selected region of the interior surface of the pipe, activating the vehicle so that it moves down the pipe at a selected speed, rotating the nozzle branches and nozzles, and applying pressurized fluid to the nozzles so that they each emit a jet that scarifies a swath of the interior surface of the pipe along the direction of travel of the vehicle.
The method may include pivoting the principal arm so that the nozzles are adjacent to a second selected region and repeating the foregoing steps.